1. Field of the Invention
The invention relates to an implement, in particular a ramming device for soil compaction.
2. Description of the Related Art
Known rammers of this type are constructed in such a way that an upper mass which accommodates a motor and a crank drive forming a motion conversion device is connected via a spring set to a working mass that essentially forms a working or compaction plate. The rotational movement produced by the motor is converted by the crank drive into an oscillating axial movement, which is transmitted via the spring set to the working plate for soil compaction.
FIG. 6 shows a rammer of this type, for example disclosed by U.S. Pat. No. 3,090,286.
According to FIG. 6, a drive shaft 1 of the rammer is driven by a motor (not illustrated) and, via a pinion 2, drives a crank disk 4 that is mounted in a rammer housing 3 and provided with external toothing. Fitted to the crank disk 4 is a crank pin 5, on which a connecting rod 6 is fitted such that it can rotate. At its other end, the connecting rod 6 is connected to a guide piston 8 by means of a gudgeon pin 7 such that it can rotate. The guide piston 8 can be moved axially to and fro, with a piston guide 9 that is fixed to it, within a guide tube 10 in a guide cylinder 11 belonging to the lower mass. This axial direction corresponds to a vertical or working direction of the implement during its use.
Arranged on both sides of the piston guide 9 is a spring set 12 comprising one or more springs, the springs in each case being supported on their sides facing away from the piston guide 9 against spring plates 13 fixed to the guide tube 10.
The guide tube 10 and the spring plates 13 belong to the working or lower mass of the rammer. A ramming foot (not illustrated in FIG. 6), which serves for soil compaction, can be fitted to the lower mass. In order to avoid the ingress of moisture and dirt, the upper mass and the lower mass are connected by an elastic bellows 14.
The guide cylinder 11 guiding the guide tube 10 is rigidly connected to the housing 3 by means of bolts 15.
During ramming operation, apart from the vibrations brought about by the acceleration of mass in the ramming system, high impact shocks occur on the rammer as a result of the ramming plate striking the soilxe2x80x94in particular in the case of very hard, stony soil. This problem is further increased in the case of relatively broad ramming plates and by the frequent crooked attitudes brought about by this and, respectively, by forces acting obliquely on the ramming plate.
The impact shocks are transmitted by the ramming plate to the guide tube and the guide cylinder and to the upper mass. As a result, they impair not only the uniform vibrational acceleration of the upper mass but can also considerably impair the durability of the parts incorporated in the upper mass, for example the bearings, the toothing systems and the motor. In addition, the impact shocks also have a negative effect with regard to the spring-mounting of the handle.
According to the invention, an implement, in particular a rammer for soil compaction or a hammer, having an upper mass, which has a drive arranged in or on a housing, having a working mass, which can be driven to and fro linearly by the drive via a motion conversion device and a spring set, and having a guide device, which is fixed to the housing and has a guide cylinder which guides the working mass linearly relative to the housing, is defined by the fact that the guide cylinder is fixed to the housing with elastic mobility, or the guide cylinder itself, given an otherwise rigid connection, has the desired elastic mobility.
The elastic mobility of the guide cylinder relative to the housing belonging to the upper mass or, respectively, the elastic mobility of the guide cylinder itself, permit effective damping of the impact shocks occurring at the working mass, in particular of the shocks which do not act in the vertical direction. Viewed from a vibration point of view, although the guide cylinder also belongs to the upper mass, according to the invention it is decoupled from the remainder of the upper mass, in order to permit the effective dissipation of force peaks.
In a particularly advantageous embodiment of the invention, one or more elastic elements are inserted between the housing and the guide cylinder. By means of suitable selection of the elastic elements, the desired elastic mobility between guide cylinder and housing can be achieved in a straightforward manner. At the same time, it is necessary to be aware that although the elements on the one hand have to provide the necessary elasticity and a corresponding possible deformation travel, on the other hand the guide cylinder still has to be connected rigidly to the housing, in order to ensure the functioning of the implement.
Therefore, a different embodiment can also be advantageous, in which the guide cylinder consists of a polymer and is connected directly to the housing without the interposition of elastic elements. Given appropriate configuration of a fixing flange provided on the guide cylinder, the required elasticity is already achieved by means of the polymer material.
In a particularly advantageous embodiment of the invention, the guide cylinder is firmly held on the housing by means of a clamping ring. The clamping ring makes it possible to interpose the elastic elements in a simple way or directly to retain the fixing flange of a guide cylinder consisting of a polymer.